The rising costs of paying for hospitals under private finance initiative schemes is bringing NHS trusts to the "brink of financial collapse" and putting patient care at risk, the health secretary has warned.

Speaking on Thursday, Andrew Lansley said he had been contacted by 22 trusts that are struggling to cope with the growing burden of the PFI contracts, a policy of the previous Labour government under which private capital is used to build hospitals and the NHS is left with an annual fee or "mortgage". Between them, the trusts run more than 60 hospitals.

However, critics have cast doubt on Lansley's claim that the legacy of PFI is the sole financial headache for the NHS in the face of a huge programme of reforms and the need to find £20bn of savings in the next three years.

In comments to the Daily Telegraph, the health secretary blamed his predecessors for the problem. "Like the economy, Labour has brought some parts of the NHS to the brink of financial collapse," he said. "Tough solutions may be needed for these problems, but we'll help the NHS overcome them."

Labour's shadow health secretary, John Healey, said Lansley was seeking to "offload the blame" for his own policies.

"The reality is that all hospitals are being forced by the Tory-led health bill to make deeper cutbacks as billions are wasted on new bureaucracy in their huge NHS reorganisation," he said.

And Dave Prentis, the general secretary of the public sector union Unison, accused the health secretary of hypocrisy.

"It's a bit rich for Andrew Lansley to complain about the cost of PFI when it was the Tories who pioneered its use in the NHS," he said. "And, against all the evidence, they are still ploughing ahead with major new projects regardless of the cost to the taxpayer.

"Unison warned right from the start that PFI is a bad deal. We said loud and clear that hospitals are shedding staff and postponing operations because they are struggling to pay off their PFI debt.

"Instead of shedding crocodile tears over the looming hospital crisis, the government should be stepping in to help. Instead they are piling on the misery by demanding £20bn from trusts in so-called efficiency savings."

PFI was first implemented under the John Major government in 1992. It was continued under Labour as a way of financing new hospitals, schools and other public sector building schemes.

The Department of Health has said there are £12.6bn of PFI contracts in the NHS, with some trusts paying their contracts off until 2050. After the recession took its toll on repayments, the annual bill is forecast to rise by 75% to more than £2.5bn over the next 18 years.

Lansley spoke about his concerns on BBC Radio 4's Today programme, saying: "If we were simply to carry on as the Labour party did in government, we would be seeing hundreds of millions of pounds every year being taken from what could provide improving services for patients in order to pay for PFI projects that roll forward for decades."

He added that patient care could be jeopardised in the areas covered by the 22 trusts. "We're looking at a risk to services in their areas," he said.

Buckinghamshire, Oxford Radcliffe, North Bristol and Portsmouth are understood to be among the trusts in difficulty.

The health secretary insisted the government needed to act in order to tackle "Labour's legacy of poor value for money", which he said included the £12.7bn national programme for IT, which is being scrapped after years of delays.

"The truth is that we have inherited in the NHS … an enormous legacy of debt – not just PFI debt, but often hospitals that are carrying substantial debts," he said.

John Appleby, the chief economist on health policy for the health thinktank the King's Fund, told the BBC that he was not persuaded by Lansley's PFI argument.

"The reason that individual hospitals get into financial difficulties are often complex, and it's not usually one single reason," Appleby said. "I have to say that, if PFI is seen to be the key problem, it doesn't augur that well for the future when … the plan is under the new government's reforms [that] the NHS will be doing deals with the private sector.

"[These deals are] not just to build hospitals but to supply health care services, a much more complicated system and a much more complicated exercise."

While admitting that PFI had proved more expensive, Appleby added that some hospitals with the schemes had remained "perfectly healthy financially"..

David Stout, the deputy chief executive of the NHS Confederation, which represents health service commissioners and providers, said: "The issue now is that the NHS is undergoing fundamental change and income for hospitals to cover the costs of PFI will become less stable, primarily because the NHS faces an unprecedented financial challenge.

"PFI contracts are long-term deals lasting up to 25 years but, in order to respond to the current unprecedented financial challenge, we will need to close some services or parts of hospitals in order to invest in more efficient services elsewhere that are better for patients.

With resources locked into PFI contracts, we will find it harder to make these vital changes. There is a real danger that we will be paying for hospitals that are not being fully used."

The Department of Health has said the government is making an independent assessment of PFI schemes. Proposals designed to ease the burden on struggling trusts could include the renegotiation of PFI contracts.

In April, the government's spending watchdog urged it to find alternative ways to fund major infrastructure projects.

The National Audit Office said the PFI scheme had become increasingly expensive since the credit crisis, and recommended that the government should consider slowing down the number of new deals it enters into.

But research published that same month suggested that the chancellor, George Osborne, has so far signed off more PFI deals than had been agreed in any of the previous three years.